/*
 * Copyright 2008 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.zxing.client.android;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.KeyEvent;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;

/**
 * An HTML-based help screen with Back and Done buttons at the bottom.
 * 
 * @author dswitkin@google.com (Daniel Switkin)
 */
public final class HelpActivity extends Activity {

	// Use this key and one of the values below when launching this activity via
	// intent. If not
	// present, the default page will be loaded.
	public static final String REQUESTED_PAGE_KEY = "requested_page_key";
	public static final String DEFAULT_PAGE = "index.html";
	public static final String WHATS_NEW_PAGE = "whatsnew.html";

	private static final String BASE_URL = "file:///android_asset/html-"
			+ LocaleManager.getTranslatedAssetLanguage() + '/';
	private static final String WEBVIEW_STATE_PRESENT = "webview_state_present";

	private WebView webView;
	private Button backButton;

	private final Button.OnClickListener backListener = new Button.OnClickListener() {
		@Override
		public void onClick(View view) {
			webView.goBack();
		}
	};

	private final Button.OnClickListener doneListener = new Button.OnClickListener() {
		@Override
		public void onClick(View view) {
			finish();
		}
	};

	@Override
	protected void onCreate(Bundle icicle) {
		super.onCreate(icicle);
		setContentView(R.layout.help);

		webView = (WebView) findViewById(R.id.help_contents);
		webView.setWebViewClient(new HelpClient());

		// Froyo has a bug with calling onCreate() twice in a row, which causes
		// the What's New page
		// that's auto-loaded on first run to appear blank. As a workaround we
		// only call restoreState()
		// if a valid URL was loaded at the time the previous activity was torn
		// down.
		Intent intent = getIntent();
		if (icicle != null && icicle.getBoolean(WEBVIEW_STATE_PRESENT, false)) {
			webView.restoreState(icicle);
		} else if (intent != null) {
			String page = intent.getStringExtra(REQUESTED_PAGE_KEY);
			if (page != null && page.length() > 0) {
				webView.loadUrl(BASE_URL + page);
			} else {
				webView.loadUrl(BASE_URL + DEFAULT_PAGE);
			}
		} else {
			webView.loadUrl(BASE_URL + DEFAULT_PAGE);
		}

		backButton = (Button) findViewById(R.id.back_button);
		backButton.setOnClickListener(backListener);
		View doneButton = findViewById(R.id.done_button);
		doneButton.setOnClickListener(doneListener);
	}

	@Override
	protected void onSaveInstanceState(Bundle state) {
		String url = webView.getUrl();
		if (url != null && url.length() > 0) {
			webView.saveState(state);
			state.putBoolean(WEBVIEW_STATE_PRESENT, true);
		}
	}

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if (keyCode == KeyEvent.KEYCODE_BACK) {
			if (webView.canGoBack()) {
				webView.goBack();
				return true;
			}
		}
		return super.onKeyDown(keyCode, event);
	}

	private final class HelpClient extends WebViewClient {
		@Override
		public void onPageFinished(WebView view, String url) {
			setTitle(view.getTitle());
			backButton.setEnabled(view.canGoBack());
		}

		@Override
		public boolean shouldOverrideUrlLoading(WebView view, String url) {
			if (url.startsWith("file")) {
				// Keep local assets in this WebView.
				return false;
			} else {
				// Open external URLs in Browser.
				startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(url)));
				return true;
			}
		}
	}
}
